Test system for a very high-speed ring network and an operating procedure for the system

ABSTRACT

A test system for a very high-speed ring network and an operating procedure for the system is provided that can be used with a communications coupler in which function tests are implemented and wherein a processor executes specific test software. The test system of the invention is also able to drive any communications coupler connected to the network, and can display the entire network on a screen of the minicomputer. The test system includes: a data processing unit with a display device for viewing the data connected through a specific link to a communications coupler that is connected to the network; a network test program running on the data processing unit; a set of function tests implemented in the communications coupler for generating frames on the network, wherein the test program controls both the communications coupler by sending it commands to perform the set of tests, and commands to display information on the status of the network as received by the coupler and sent by the coupler to the processing unit. The test system of the invention is applicable to FDDI or TPDDI networks.

FIELD OF THE INVENTION

This invention relates to test systems for high-speed ring networks, andparticularly to a test system for data transmission networks of the FDDIand TPDDI types.

BACKGROUND OF THE INVENTION

Optical fiber networks are increasingly common, and are standardized byinternational standardization committees such as American NationalStandards Institute (ANSI) under reference number X3T9-5. These samestandards have also been adopted by the International StandardsOrganization (ISO). They are also included in the definition of typeTPDDI networks which currently tend to be used in local area networkswhere the transmission distances between the various stations orterminals are relatively short.

Information messages sent by the various stations of a network consistof a plurality of frames. A frame includes data bracketed in time bysignals placed at the beginning and the end of the frame, such signalsbeing called "control characters".

In addition, the components of a computer system (processors, RAM, ROM,controller, etc.) are mounted on a set of boards of dimensions that havebeen standardized. These boards are usually connected to a singleparallel bus for providing communication between the various elementsmounted on the boards, conveying data between them, and providingelectrical power.

A computer of this kind is connected to an FDDI or TPDDI network througha gateway connecting device for adapting the data transmissionconditions on the computer bus to the transmission conditions on thenetwork in question.

FIG. 1 shows the general structure of a gateway device DPC of this kind,and a computer ORD whose several component elements are mounted on aplurality of boards C communicating with one another through a bus PSB(parallel system bus). Each board C is connected to the PSB through aconnecting interface IC. The type of connecting interface and the mannerin which it communicates with the other functional components of thecomputer depend on the type of bus used. Generally the bus andconnecting interface are precisely defined by standards (for example,the standards applicable to the MULTIBUS II bus, defined by standardIEEE1296).

The computer ORD is connected to a network RE in the form of a ring, ofthe FDDI (or TPDDI) type, for example, through a gateway connectingdevice DPC. Network RE includes a main ring AP and a secondary ring AS.

The gateway device DPC includes a universal coupling device GPU, acommunications coupler FDI, and an interface IHA to transfer informationbetween the GPU and the FDI.

The universal coupler GPU is connected to the PSB through a connectinginterface IC, usually of the same type as the IC interfaces describedabove and associated with the boards C.

The gateway device DPC is physically connected to the network RE througha device DA that provides physical access to the network, associatedwith the communications coupler FDI.

The general structure of the device DPC as shown in FIG. 1, as well asthe structure and function of the two elements GPU and FDI included init, are described in detail in French Patent Application 89 10 156,filed Jul. 27, 1989 under the title "Gateway Device for Connecting aComputer Bus to a Fiber-Optics Ring Network"; corresponding to U.S.application Ser. No. 07/877,254, filed Apr. 28, 1992, a continuation ofU.S. application Ser. No. 07/557,519, filed Jul. 24, 1990, nowabandoned.

A test system can be connected to network RE by a communications couplerFDIT identical to communications coupler FDI of the gateway connectingdevice DPC. This is why it is useful to recall the essential componentsof such a communications coupler, it being understood that a moredetailed description of the latter as well as its operation can be foundin the French Patent Application 89 10 156, filed Jul. 27, 1989, hereinincorporated by reference.

Referring to FIG. 2, the communications coupler FDI is connected touniversal coupling device GPU through interface IHA, itself including aninterface IHAC for the control characters and an interface IHAD for thedata to be transmitted, also referred to as useful data.

Interface IHAC includes a part EC for sending the control characters anda part RC for receiving the control characters of frames coming from thenetwork.

Interface IHAD includes a part ED for sending useful data of framesdestined for the network RE and a receiving part RD adapted to receivethe useful data of frames coming from the network RE.

The communications coupler FDI includes:

a transfer management controller CGT for use with a microprocessor MPassociated with a group of slave elements SERV (RAM or EPROM memory,couplers, etc.) The management controller CGT is associated with acontrol bus BC to which elements MP, SERV, and interface IHAC areconnected;

a network access controller CAR, in turn connected to a device DA forphysical access to the network and to control bus BC;

a high-speed bus BHD (capable of carrying frames at rates on the orderof 100 megabits per second), connected to interface IHAD and to networkaccess controller CAR; and

a storage memory MST connected to high-speed bus BHD and to networkaccess controller CAR through a control line LC (including control wiresfor writing to and reading from the memory, as well as information foraddressing the latter).

Now consider the transmission of a given frame from the computer ORD.After passing through universal coupling device GPU the frame arrives atthe interface IHAC, in the form of useful data sent to part ED ofinterface IHAD, and a control block sent to part EC of interface IHAC.These control blocks include control characters relating to the contentof the frame in question as well as information relating to the natureof the operations to be performed on this frame by the communicationscoupler FDI.

Management controller CGT reads the control blocks in interface IHAC andinterprets them to form control characters in accordance with the FDDIstandard relative to the frame in question. As soon as these controlcharacters have been formed, they are sent through bus BC, controllerCAR, and bus BHD to storage memory MST. During this time, themicroprocessor MP manages the transfer of useful data from the frame tostorage memory MST. As soon as the control characters and useful datahave arrived in the memory, network access controller CAR, under thecontrol of microprocessor MP, sends the frame thus formed to network RE.

It is clear that a process exactly opposite to that just described takesplace during reception of a frame of the FDDI type coming from thenetwork RE.

The existence of two separate buses BC and BHD for the control blocksand for the useful data, respectively, makes it possible to transfer thecontrol blocks on bus BC independently of the corresponding useful dataon bus BHD, and the control block can be transferred on its bus before,at the same time as, or after the corresponding useful data have beentransferred on the bus BHD. The recent appearance of FDDI or TPDDInetworks requires test tools that provided engineers or users of thesenetworks with the following functions:

traffic generation (generation of frames): this function is needed forqualification of specific devices, such as communications couplers likethose shown in FIG. 2, or the wiring of such communications couplers, orthe group of transmission media;

display of the network: the FDDI standard provides for obtaining fromany station, information on the status of the network at a given moment,including the load rate of the network, the error rate, the number offrames in circulation, etc. It is therefore useful to display on ascreen the status of the network on the basis of this information; and

compliance test: all FDDI-type devices must obey the standard, i.e.,they must offer a given number of services. It is therefore necessary tohave a tool capable of checking the existence and correct operation ofsuch services. Among the latter are in particular the frames called SMT,defined in standard FDDI.

It would be desirable to provide a test system that meets therequirements listed above, and can be used with a communications couplersimilar to that in FIG. 2 in which function tests are implemented (inslave elements SERV) (generation and reception of traffic . . . ) and aminicomputer of the PC type (personal computer) running specific testsoftware. It would also be desirable for this test system to be able todrive any communications coupler connected to the network, similar tothe communications coupler FDI as shown in FIG. 2, and to display theentire network on a screen of the minicomputer.

SUMMARY OF THE INVENTION

A test system for a high-speed ring network is provided that includes adata-processing unit equipped with a data-display device, connectedthrough a link to a communications coupler connected to the network; anetwork test program running on the unit; and a group of function tests,implemented in the communications coupler, for generating frames on thenetwork, the test program driving the communications coupler by sendingit commands that perform the set of tests, and commands to displayinformation relating to the status of the network, as received by thecoupler and sent by the coupler to the processing unit.

The test system of the invention meets the requirements listed in thebackground of the invention, and can be used with a communicationscoupler similar to that in FIG. 2 in which function tests areimplemented (in slave elements SERV) (generation and reception oftraffic . . . ) and a minicomputer of the PC type (personal computer)running specific test software. The test system of the invention is alsoable to drive any communications coupler connected to the network,similar to the communications coupler FDI as shown in FIG. 2, and candisplay the entire network on a screen of the minicomputer.

BRIEF DESCRIPTION OF THE DRAWING

The invention will be more fully understood from the following solelyexemplary description of a preferred embodiment taken in conjunctionwith the accompanying figures in which:

FIG. 1 is a block diagram that shows how a computer is connected to anetwork through a communications coupler, and also shows how the testsystem of the invention is connected to this network;

FIG. 2 is a block diagram that shows the essential components of acommunications coupler as described in the patent application referredto above;

FIG. 3 is a block diagram that shows the essential components of thetest system of the invention;

FIG. 4 is a block diagram that shows how the communications coupler ofthe test system is connected to the link to the minicomputer through aplug-in board;

FIG. 5 is a block diagram that shows the general structure of the testprogram of the test system of the invention, running on theminicomputer; and

FIG. 6 is a screen display showing a plurality of pull-down menus.

DESCRIPTION OF A PREFERRED EMBODIMENT

With reference to FIGS. 1 and 3, the test system ST according to theinvention is shown in FIG. 3 and includes a test case VT connected by alink L specific to a minicomputer PC. This link is of the standard RS232type. It is connected to minicomputer PC through a standard connectorCN₂ and is connected to case VT by a connector CN₁ of the same type asCN₂.

Minicomputer PC includes in particular a display screen VD and a diskmemory DISC having either a hard disk or a floppy disk on which the testsoftware running on the PC is permanently recorded. The computer can beany kind of minicomputer currently available.

Test case VT includes a communications coupler FDIT of the type that issimilar in every respect to FDI of FIG. 2, with the power beingfurnished by a power supply ALIM and connected through a physicaladaptor DAT similar to DA to network RE.

Slaves SERV and FDIT contain a set of function tests ETF implemented bythe microprocessor MP upon receiving commands from the minicomputer PC(which in this case assumes the role played by the CPU for a board(FDI). This assembly generates traffic on the network RE by sendingpredefined frames in accordance with FDDI standards (e.g., of the typeLLC, SMT, or NIF, as discussed below), receiving frames of the same typecoming from the network RE to display their contents, receiving andresending these same frames in the ECHO mode, as defined for testsnumber 3 and number 4 explained in detail below.

Note that FIG. 1 shows the functional diagram of the test systemaccording to the invention, while FIG. 3 shows the physical arrangementof each of the elements constituting the test system.

Test case VT is in the shape of a parallelepipedic suitcase and isreadily transportable by a manual operator.

Communications coupler FDIT is connected to link L by means of aconnector CN₁ which is itself mounted on a plug-in board CB.

With reference to FIG. 4, the plug-in board CB is connected tocommunications coupler FDIT by an interface IHAD similar to IHA and bycontrol memory MC and interface IHAC. FIG. 4 also shows in greaterdetail how interface IHT is connected to plug-in board CB. Plug-in boardCB makes it possible to connect parts ED and RD of IHAD through aplurality of wire connections F₁ to F_(n) and the amplifier circuit, andto reform them as A₁ to A_(n), with wire connections F₁ to F_(n) beingconnected in series respectively with amplifier circuits A₁ to A_(n).Thus, transmitter section ED is looped back to part RD so that a framecoming from network RE and reaching part RD through bus BHD is sent outagain on section ED and then on bus BHD to memory MST and is then sentback out into the network again.

Connector CN₁ is connected to a control memory MC which is itselfconnected to each of the two parts EC and RC of IHAC and to control busBC (and hence to MP) by a bus BMC. MC belongs to FDIT. Similarly,coupler FDIT can be coupled:

either to minicomputer PC (by plug-in board CB), in which case it is anintegral part of test system ST. In this case, the control blocks sentfrom minicomputer PC through L and CN₁ are initially stored in MC beforebeing sent out on BC to be analyzed by MP; IHAC is not used. MC thenperforms the series-parallel conversion between series link L and busBC, or

directly to the GPU, in the absence of a plug-in board CB, in which caseFDIT acts as the communications coupler of a normal FDDI station. IHA isthen connected to the data bus of GPU and memory MC is connected to thecontrol bus of the latter. IHAC is then used and MC merely stores thedata temporarily before they are transferred to IHAC.

In the following, therefore, we will assume that FDIT is associated withST. Minicomputer PC and the communications coupler then exchange betweenthem only the control blocks and no useful data.

To test the network RE shown in FIG. 1, it is sufficient to insert intothe network, apart from test system ST, a second test system ST₁. It isthen possible to check whether everything that has been sent by one ofthe two test systems, ST for example, has been correctly received by theother system ST₁, and vice versa. It is also possible to capture one ormore frames to check on their condition. To perform a valid test, thenetwork is loaded 100%, and a check is made to determine whether allconnections have been made correctly, and that there is no problem withoptical transmission, if a network of the FDDI type is involved, andthat the specific stations including communications couplers such as FDIare functioning correctly, as well as all their components, during thetest.

FIG. 5 illustrates the structure of the test program LOGT running onminicomputer PC. This program LOGT is built around a window generatorGF, with the windows that it creates being designated by F₁ to F_(n).The fact that GF generates windows F₁ to F_(n) is symbolized by thegroup of arrows P₁ to f_(n) connecting it to the corresponding windows.

In addition, the program LOGT includes four levels N₁ to N₄. The firstlevel N₁ defines the skeleton SQ of the program: this skeletonspecifically allows dimensioning of the windows, defining their treestructures, i.e., the way in which they link to one another, and definesthe procedure calls. It is at this first level N₁ that window generatorGF makes its call to construct the different windows F₁ to F_(n). Theyare constructed using a root menu included in this skeleton.

The second level N₂ describes the various commands that can be sent toall the communications couplers of the FDI type as well as to any FDITboard of any test system ST connected to network RE. This second levellikewise describes the structure of the responses to these differentcommands that are received, the responses relating primarily to thedisplay of the status of the various elements constituting a board FDI,the status of the various counters included in it, etc.

The third level N₃ executes predefined functions: these functionsspecifically display the entire ring forming network RE and also displaywhat is occurring inside each communications coupler of a stationconnected to this ring.

The last level N₄ permits rapid programming of the FDIT board of testsystem ST.

In the exemplary embodiment described here, there are 40 possiblewindows numbered from 0 to 39, i.e., windows F₀ to F₃₉. Each window hasa maximum of 23 fields C₀ to C₂₂, each field being identified by adescription with a maximum width of 19 characters.

Three types of actions are associated with a given field of a window:

calling another window, which window is then identified by its number(from 1 to 39, with 0 conventionally signifying that this window doesnot define a specific action, and with window 0 actually including theroot menu of test program LOGT);

calling a function identified by a subscript (in the embodimentdescribed here, this subscript is larger than 1,000). This function isoperated by a specific program (at level N₃); and

defining a datum with a maximum width of nine characters. The width isthen defined by a subscript between -1 and -9 (with -1 corresponding toa width of one character and -9 to a width of nine characters). The term"character" on a computer screen means either a letter, a number, or apunctuation mark or symbol. Each character corresponds to a knowncombination of a fixed number of bits (eight for example).

On the screen of the minicomputer, the upper left corner position of awindow is defined by two coordinates X0 and Y0, where X0 is between 0and 79 and Y0 is between 0 and 24. If X0 and Y0 are equal to -1 theposition of the window on the screen is determined by the LOGT program:this signifies that when one window calls another, LOGT tries to placethe latter near the former so that the appearance of both of them on thescreen will appear simple and clear to the human operator working on thescreen.

FIG. 6 shows a screen of minicomputer PC and illustrates the definitionof a window by means of a function called BUILD. The definition of thewindow in question, namely the window numbered 10, i.e., window F₁₀, isaccomplished with the aid of a part of window F₀ that calls the rootmenu of LOGT as well as three windows F₁, F₂, F₃ all of which call thefunction BUILD to define the window in question, specifying its formatand describing it by indicating primarily the number of the field, itswidth, etc.

Window F₃ can also call the COPY function (see below). Each of windowsF₁ to F₃ can be reprogrammed at any time by the function BUILD, therebyredefining its length, the number of fields, their width, etc.

Thus, referring to FIG. 6, it can be seen that an attempt is made toconstruct a window labeled "10" using the function BUILD, with a fieldnumber of 10, whose width is ten characters each, with the positioningof the window being controlled by the program such that X0 and Y0 bothare set to -1. The field whose description is "EXEC" calls the functionof subscript 1100, with the field with the description "FORMAT" callingwindow 30, while the field with the description "FAMILY" is associatedwith a datum four characters wide. All the fields whose descriptionsappear at the upper right in FIG. 6 also have a width of fourcharacters.

There are also other functions that relate to level N₁. These are thefunctions labelled as follows: "SAVE", "COPY", and "BOOT". The first ofthese loads or saves a configuration of the entire test program LOGT ata given moment, i.e., the group of 40 windows available in a specialmemory of the PC, the memory being of the RAM type, for example. Thesecond recopies a source window to a destination window, with thewindows being identified by their numbers. This function thus recopiessource window F₂₅ to destination window F₃₅. The third creates ormodifies a particular file containing the name of a configuration fileloaded during execution of the LOGT program: it therefore memorizes thecontents of 40 windows at a given moment. When the program isrelaunched, the resultant configuration is the one it had when it left.

Now let us consider level N₂ regarding the sending of commands to theFDIT board and the display of the responses corresponding to thesecommands: this operating mode allows transmission of a command to theFDIT board through the RS232 link, and then display of the responseobtained on the minicomputer screen.

To create and execute a given command, three windows are required:

a) The window of the "COMMAND MESSAGE" containing the command message tobe sent to the FDIT board (PC and FDIT exchange only command messages).This type of window, in the embodiment described here, has a numberbetween 10 and 18.

b) The "FIELD" window shows the field number of the expected response.It is one of windows F₂₀ to F₂₈.

c) The "FORMAT" window describes the display format of the variousresponse fields, the display format on the screen of the minicomputer.This window is one of windows F₃₀ to F₃₈.

The "COMMAND MESSAGE" window therefore contains a command message, asstated above. The message is written in sixteen-bit words, inhexadecimal code. The most significant eight-bit byte, associated withthe "HEADER" field, represents the command code, while the low-ordereight-bit byte indicates its length (the latter is expressed ineight-bit bytes). The sixteen-bit word corresponding to the "HEADER"field is placed at the head of the message. The "HEADER" field isfollowed by other fields containing the other command data, and adescription recalling the interpretation for each field located behindthe "HEADER" field.

The "FIELD" window describes a response structure and indicates thefield number of the response as well as the size of each field expressedin eight-bit bytes, with the legal values in the embodiment describedhere being 1, 2, and 4.

The "FORMAT" window describes the display format of a response field andthe associated description. The FORMAT code is identical to that of thewell-known C language function, namely "PRINTF". The display format istherefore one that is normally used in minicomputers.

The usual commands in the embodiment described here are the following:

The connection command, also called the "CONNECT" command, allows theFDIT board to be inserted into the network RE, with a specific fielddefining the operating mode of the board.

The disconnect command "DECONNECT" allows the FDIT board to bedisconnected from the network RE. It therefore cancels out the effectsof the CONNECT command.

The "SEND-FRAME" command causes a frame of type SMT to be sent, withthis type of frame being defined in the above-mentioned ANSI standard.The definition of the SMT frames in fact constitutes a subset of theFDDI standard as defined by ANSI. This frame is sent by FDIT over thenetwork and is recovered by the corresponding board of test system ST₁which sends a response frame of type SMT. The response frame isdisplayed on the screen in hexadecimal form. This command is used duringinteroperability tests of the network RE.

The initialization command "INIT-PTCOL" initializes the parameters oflevel MAC (medium access control), with the latter being defined in theFDDI standard. These parameters are the minimum value of the rotationtime in the ring (target token rotation time), whose symbol is TTRT,defined by the standard, and less than 4 milliseconds long. This samecommand likewise defines the maximum value of this same TTRT, which mustbe less than 165 milliseconds. This command likewise defines the desiredvalue of the rotation time of the token in the ring during theinitialization of the level MAC, this value being between the minimumand maximum values of the TTRT. Other parameters of this kind are thosethat define whether there is or is not a priority assigned to theasynchronous traffic; whether board FDIT must receive all the frames oronly the valid frames; whether operation is in the long-address or theshort-address mode (these two modes are likewise defined by the FDDIstandard). They are also the short-group address of the station whenoperating in the short-address mode, or the short-address of thestation, and the long address of the station, when operating in thelong-address mode.

The "SET-VALUE" command is used to modify a parameter of the SMT type ofboard FDIT or any other FDI board of any station in the network RE. Thiscommand is executed in two stages:

a request from a transaction identifier to the station affected by thischange of parameters; and

sending the new parameter value to the station in question, through aspecial frame specified in the FDDI standard.

At the end of this two-stage operation as outlined above, a parameterlikewise specified in the standard is displayed and reports the successor failure of the operation. The entire two-stage procedure outlinedabove is in accordance with standard SMT 6.2of the FDDI standard.

The "RESET" command resets the FDIT board during operation or any otherFDI board of a station connected to the network RE, without having toperform from the beginning all of the operations of the BIST (BUILD-INSELF-TEST) type, known in current practice and which involveinitialization of all the components on a given board, in this case FDITor FDI boards.

The "STATUS" command provides information on the status of the FDITboard or any FDI board connected to the network at a given point intime. This information may relate, for example, to the number ofeight-bit bytes received or sent per second, and the status of certainrobots defined in the FDDI standard and which are always present in thecommunications couplers, the robots being of the CFM, PCMB, or PCMA typefor example. From the status of these robots one can determine certaininformation on the status of the corresponding board, for examplewhether the two connections from the board to the network RE are activeor not. One can also obtain information about the status of thecomponents constituting elements CAR and DA of boards FDI or FDIT inFIG. 2, and more specifically the components marked CMS, CCD, and FORMACwhose roles are defined precisely in the French Patent Application 89 10156, filed Jul. 27, 1989.

The "SET-TEST" command places either FDIT boards or any other boards FDIin different test configurations. There are five types of tests, withtests 1 to 4 being of the functional type, i.e., verifying correctoperation of the board, while test 5 is of the operational type, morespecifically dedicated to generating traffic on the network RE.

These various test modes are as follows:

Test Number 1: this is the receiver test, used to check the operation ofan FDI board (or an FDIT board) when receiving frames of the LLC type(defined by the FDDI standard). These frames include data to be carriedand are used in the network. For this test, board FDIT sends one frameor several frames of the LLC type over the network RE and checks to seewhether the FDIT board of the second test system connected to thenetwork, namely system ST₁, is receiving these frames correctly. Thetest can also be used to check whether any other FDI board is receivingthe frames sent by the first FDIT board correctly.

Test Number 2: This test checks the function in the send mode of all theFDI boards (or FDIT boards). The FDI board under test then sends framesof a specified length. These are sent in the form of several blocks offrames sent in a given time interval. These frames can be LLC frames ofthe asynchronous or synchronous type, with a short or long address. Oncethey have been sent by the board whose send function is being checked, adetermination is made using the FDIT board of test system ST that theyare correct, assuming that the FDIT board is in good operatingcondition, as well as the support system for network transmission.

Test Number 3: This test checks the correct operation of any FDI (orFDIT) board. It is called the local repeater test. It operatesspecifically when the optical transceivers on the board in physicaladaptation device DA (see FIG. 2) are looped back on themselves with afiber length greater than 1 kilometer. To perform this test, a frame ofthe asynchronous type with a short address is addressed by ST (and thusin fact by FDIT) to the FDI board of the station under test. This framesent to the FDI is repeated by the plug-in board in the latter and sentback out; onto the network where the FDIT board verifies that the framethus sent is in good condition. In this particular test, the length ofthe frame data field is eight-bit bytes. This test is then initializedby ST.

Test Number 4: This test is called the repeater test, and resends allthe frames (except SMT type frames) addressed to the FDI board undertest, from the latter to the stations that sent them. This test is notinitialized and cannot run if the frames are sent over RE by any one (orseveral) station(s).

Test Number 5: This test, called the operational test, uses the FDITboard as a traffic generator on the network and/or as the networkadministrator.

For all of Tests 1 to 5, a certain number of parameters must be definedthat will be contained in the fields of windows calling these varioustests: they include the short destination address (sixteen bits forframes sent in tests 2 and 5), a parameter that authorizes or inhibitssending of test frames and shows the counter values contained in the FDIboards (in slaves "SERV"), during a test between two stations connectedto the network, a parity parameter, a parameter defining the size of theframes sent in eight-bit bytes (for Tests 2 and 5), the value of thequantity Fc (frame control, part of the control characters) for framessent in Tests 2 and 5, a parameter defining the depth of the FIFOs usedin 32-bit words for the FIFO memories constituting interfaces IHAC andIHAD (see FIG. 2), a parameter indicating whether the station under testis one with a single or double connection to the network, and aparameter defining the transmission frequency of frames NIF, expressedin seconds, the frames NIF likewise being defined in standard FDDI. Thelatter parameter directly controls the time needed to acquire the newnetwork configuration during a station connection for example. Otherparameters are required, for example the long destination address of theframes sent during Tests 2 and 5, the wait between transmissions ofblocks of frames between 0 and 2 seconds, and the number of frames thatcan be sent in a "BURST" in Tests 2 and 5.

The "COLLECT-MA" command reassembles the data contained in a group ofcounters at the "medium access control" level. These counters are partof slaves SERV of controller CGT shown in FIG. 2. The data relating tothe total number of frames on the ring, the number of frames lost, thenumber of frames containing errors, the number of frames sent andreceived by the destination without any errors, the number of framessent but with problems (addressee absent for example), the number offrames sent but not recognized by their addressees, the number of framessent and seen on the ring with an error FCS, the number of framesreceived with or without errors, the number of frames sent and notcopied by the addressee, the number of frames received with errors FCS,the number of frames received whose addresses were recognized by otherstations, etc. (FCS=frame check sequence, defined by standard FDDI, theset of bits located at the end of the frame for error detection) can allbe collected.

The "GET-VALUE" command gets the value of a parameter or a group ofparameters. It can be intended either for an FDIT board or for any otherFDI board of a station connected to the ring. In this case the commandis sent in SMT form (according to standard SMT 6.2).

The "GET-VALUE" and "SET-VALUE" commands are executable on any stationin the network, whether the communications coupler is the type with anFDI board shown in FIG. 2 and described in the abovementioned Frenchpatent application, the type with an FDIT board, or a communicationscoupler of any type. These commands conform to standard FDDI.

Alternatively, commands such as "RESET, " "STATUS, " and "COLLECT-MA"are sent on the network in the form of SMT frames and are ignored bycommunications couplers other than FDI. They are therefore destineduniquely for tests of FDI boards.

The "CONNECT", "DECONNECT", "INIT", and "PTCOL" commands can be executedonly on the FDIT board. These latter commands are coded with adestination field of zero. The special commands mentioned above arecoded with a destination address field equal to zero if they areaddressed to station FDIT of the test system, or equal to the address ofthe addressee in the contrary case (other FDI board).

To connect an FDI board to be tested, the following functions must beperformed after powering up the board:

"INIT-PTCOL": to initialize the MAC parameters of the board;

"SET-TEST": to select a specific test, one of Tests 1 to 5; and

"CONNECT": to connect the board in question to ring RE.

All modifications to the test (shifting from one test to another) implyprevious disconnection of the station from the network, using the"DECONNECT" command. After selecting the test to be performed (using the"SET-TEST") command, the "CONNECT" command reinserts the board in thering.

In the event of an error in test operation or on the board, the "RESET"command reinitializes communications coupler FDI. Then the threecommands listed above must be used to reconnect the board to the networkRE.

One specific function called "AUTOEXEC", which is in fact a specificcommand, repeatedly executes a series of commands (a maximum of threecommands). It can be used for example to connect and disconnect astation to and from the network periodically during the reconfigurationtest. One specific field then defines the time interval separating thetransmissions of two successive commands. The minimum value of thisfield is zero, with the maximum value of 20 corresponding to one secondof time. The commands are selected by setting the given field associatedwith the name of the command to a value of 1.

As can be seen from the above, level N₃ contains a certain number ofpredefined functions. These functions respond to two types of needs:

display of the activity of an FDI board (configuration, charge rate,error rate, etc.); and

display of the activity of the network and specifically of any FDDI typestation using methods that conform strictly with the FDDI standard.

These functions permit access through the FDIT board to all the stationson the network, of either the FDI or another type.

The principal ones include the following:

The "BUILD-MAP" function acquires the list of addresses MAC of thestations on the network, and memorizes them permanently. This list ofaddresses is then used by the other functions to select a specifictarget station. These MAC addresses are obtained through frames of theNIF type. As they are obtained, one specific window displays the addressof the interrogated station (target station) and the desired (address ofnext station). This function operates by going around the ring,searching for the address of the next station in turn, throughsuccessive approaches;

the "VIEW STATUS" function displays the status of the FDI board and usesparameters that do not exist in the FDDI standard. It is thereforestrictly reserved for couplers of the FDI type. The list of displayedparameters, which is not exhaustive, can be as follows:

configuration: displays the status of the station (not FDDI), whetherthe station includes one or two active attachments or none.

charge on the station during transmission and reception in megabytes persecond (not FDDI);

number of frames sent and received, number of frames not copied, numberof frames on the ring, number of frames with errors, number of frameslost, contents of error counters on optical receivers, contents of errorcounters on optical receiving buffers (all the parameters listed aboveare defined by the FDDI standard), contents of error counters relativeto frame reception (not FDDI), number of times the ring becameoperational, number of expirations of token counter (FDDI standard). Thetoken counters and error counters are contained in slaves SERV ofcontroller CGT (FIG. 2).

The "STD-VIEW" function: this function displays a station usinginformation obtained from the frames called "SIF-0" and "SIF-C" inaccordance with standard SMT 6.2.

The "SIF-CONFIG" function and the "SIF-OPER" function serve respectivelyto display the contents either of a SIF frame called the configurationframe or of a SIF frame called the operating frame, the framesconforming to standards SMT 5.1 to 6.2. They are used mainly ininteroperability tests.

The "VIEW RING" function generates an image of the double ring usingframes NIF, SIF-0, and SIF-C in accordance with standard FDDI. The imageof the ring thus generated includes a maximum of 15 stations. Stationconfiguration is shown in graphic form, displaying the primary ring inone color, and the secondary ring in another (green and red, forexample), for the specific fields called Tx and Rx, indicating thenumber of frames sent and received per second by the station. Thisinformation is refreshed periodically so that the reconfigurations canbe determined in real time. Other functions make it possible for exampleto receive and display images sent by any station of type FDI, toreinitialize series link RS232 from the FDIT board, to acquireperiodically one or several SMT parameters allowing the collected valuesto be displayed in graphic form on screen VD of computer PC.

The "CATCH" function is used to read a frame received by any FDI boardusing the FDIT. It is executed in two-stages:

initializing the frame capture parameters: for this step, the followingparameters must be known: the address of the addressee of the command,the value Fc of the frame captured, and the address of the sourcestation of the captured frame; and

reading from the buffer memory of board FDIT. After reading, the capturemode is automatically reset, with the parameters defined beforehand bythe initialization stage.

If none of the frames is captured, a message indicating that no framewas captured is displayed on the screen.

The capture buffer memory can memorize up to 128 eight-bit bytes ofdata. When the data field of the captured frame exceeds this size, amessage indicating that the captured frame is incomplete is displayed onthe screen. Reading the capture buffer memory reveals flags EAC(according to the FDDI standard) of the frame received, its length fromcharacter Fc to FCS inclusive, the frame destination address, the framesource address, and obviously the useful data of the latter from thesource address to the final character of frame SCS, inclusive.

Another function associated with level N₃ is used to display a stationas well as its physical neighbors. This function is called the topologyfunction.

Level N₄ is called the fast or "FAST" mode and is used for rapidprogramming of the FDIT board. This mode is used to access all thefunctions of level N₃ as well as an extremely rapid initialization ofthis board using the minicomputer keyboard. The user can modify theparameters as desired. The parameters thus modified and memorized in thewindows corresponding to the functions of level N₂, making it impossibleto save the desired configuration (before modification of the userparameters) in an appropriate file.

A number of keys on the board, called direction keys, allow preselectingthe desired function. Another button activates the desired function,while a third button quits a function when desired.

Other modifications and implementations will occur to those skilled inthe art without departing from the spirit and the scope of the inventionas claimed. Accordingly, the above description is not intended to limitthe invention except as indicated in the following claims.

What is claimed is:
 1. A test system (ST) for a high-speed ring network(RE), the test system comprising:a data processing unit (PC) equippedwith a data display device (VD) connected through a link (L) to acommunications coupler (FDIT) connected to the network, transferringdata frames thereon the communications coupler comprising:a transfermanagement controller (CGT) including a microprocessor (MP) and a set ofslave elements (SERV) with a set of function tests, the transfermanagement controller being associated with a control bus (BC) to whichthe microprocessor (MP), the set of slave elements (SERV), and aninterface (IHAC) are connected; a network access controller (CAR) inturn coupled both to a device (DA) for physical access to the networkand to the control bus (BC); a high-speed bus (BHD) coupled to theinterface and to the network access controller (CAR); and a storagememory (MST) coupled respectively to high-speed bus (BHD) and to thenetwork access controller (CAR) through a command line (LC), the controlbus carrying control blocks including control characters that relate tothe constitution of the frames, and information relating to the natureof the operations to be performed on each frame by the communicationscoupler, the high-speed bus carrying the useful data from the framescorresponding to control blocks carried on the control bus, and themanagement controller being for reading the control blocks andinterpreting them to form the control characters that frame the usefuldata of the frames to be sent on the network, and for forming controlblocks to be sent to the data processing unit, beginning with thecontrol characters framing the useful data of a frame coming fromnetwork (RE); a network test program (LOGT) running on the dataprocessing unit; and a set (ETF) of function tests implemented incommunications coupler (FDIT) for stimulating the transfer of testframes on the network, the test program (LOGT) both controlling thecommunications coupler by sending it commands that allow running the setof tests, and also the test program controlling the communicationscoupler by displaying data on the status of the network, such as datareceived by the coupler and sent by the coupler to the processing unit.2. A test system (ST) for a high-speed ring network (RE), the testsystem comprising:a data processing unit (PC) equipped with a datadisplay device (VD) connected through a link (L) to a communicationscoupler (FDIT) connected to the network; a network test program (LOGT)running on the data processing unit for use with a window generator (GF)for generating a plurality of windows F₁ to F_(n), and including atleast three levels N₁ to N₃, whereinthe first level N₁ defining theskeleton (SQ) of the program for constructing the different windows; thesecond level N₂ describing a set of commands sent between stations onthe network, as well as respective structures of the responses to thecommands; and the third level N₃ performing predefined functions thatpermit displaying the entire network (RE), as well as displaying what isoccurring within each communications coupler of a station coupled to thenetwork (RE); and a set (ETF) of function tests implemented incommunications coupler (FDIT) allowing frames to be generated on thenetwork, the test program (LOGT) both controlling the communicationscoupler by sending it commands that allow running the set of tests, andalso the test program controlling the communications coupler bydisplaying data on the status of the network, such as data received bythe coupler and sent by the coupler to the processing unit.
 3. The testsystem (ST) of claim 2 wherein each window comprises a given maximumnumber of fields (C₀ to C₂₂), each field being identified by adescription of a maximum predetermined width, three types of actionsbeing capable of being associated with each of these fields:a call foranother window, identified by a given number between 1 and n; a call fora function identified by a given subscript, run by a specific programbelonging to third level N₃ ; and a definition of a datum having amaximum width that is known in advance.
 4. The test system (ST) of claim3 wherein three windows are employed to perform a command determined bylevel N₂ :a command message window containing the command message to besent to communications coupler (FDIT) by data processing unit (PC); afield window indicating the number of fields of the anticipatedresponse; and a format window describing the display format fordifferent fields of the response on the display device (VD).
 5. The testsystem (ST) of claim 3 further comprising:a command for placing thecommunications coupler in one of a plurality of test configurations,including test configurations of the functional type for allowingchecking of the correct function of a communications coupler other thanthe communications coupler connected to the data processing unit, andtest configurations of the operational type for generating traffic onthe network.